Because of the faulty rear control arm in the 2006-2008 HCH, all 4 of my tires were cupped and I had to replace them with 4 new tires (see previous post on this).

When you put on 4 new tires, does your MPG suffer for a while? Will it come back again as the tires "wear in?"

I didn't want to put on the same crappy Dunlops that came with the car (2006 HCH), which have a terrible treadwear rating and no mileage warranty. I was looking at the various LRR (Low Rolling Resistance) tires that are out there, and most were WAY too expensive for me (even from the cheapest place out there -- tirerack.com, the Michelins were just under $120 each, as was the new Yokohama Orange Peel tire that's environmentally friendly as well as LRR). That's just the price for the tire (before shipping, before installation, before tax, etc). I was going to put on just a normal (non-LRR) all season tire (the Yokohama Avid Touring S) and then at the last minute decided on the Goodyear Assurance Fuel Max. The Fuel Max is supposed to be an LRR tire.. in fact they advertise that you'll get 2600 extra miles savings of gas with the tires during the normal lifetime of the tire (I'm sure that's inflated, but nonetheless, it's designed to be an LRR tire). Interestingly, the car they used to get that figure (which they say is 4% in their press releases) was the (normal) Honda Civic. Goodyear also makes the OEM tires for the Prius... so I figured OK. Tirerack had them for $79 each, and a local place matched what would've been the final price had I gone through Tirerack and one of their local installers (which was $433 out the door).

Had the tires put on, then went immediately over to the dealership so they could replace the faulty-designed original rear control arm with the corrected one (so the new tires won't cup the way the old ones did), they did a free 4 wheel allignment as well (part of the repair package for the problem). So I have 4 brand new tires, and a complete allignment.

But I've noticed the first 2 days of driving it that my MPG has gone down. Nothing else changed (same tank of gas, same everything else). I'm looking at the "real-time" MPG meter, not the long-haul odometer. But in places that I've driven with the HCH almost every day for the past 3 years, the MPG seems definitely to be lower. In sections where I always get right at the 50 mark on the real-time MPG meter, it was getting under it, and this was a constant thing. About 10-15% less maybe. These are supposed to be LRR tires, fuel-saver tires (with fuel saving results done on a Honda Civic). Same exact size tire as spec, etc.

Just wondering if it's normal with ALL new tires that your MPG will go down at first until they're worn in, or if this is something that'll remain the same as long as I have these tires. I mean, heck, I could've just bought the Yokohamas for $100 less if I didn't want to get an energy-saving tire. So that's why I'm wondering if I just threw the $100 away or if it'll improve back to normal in time ("normal" being having 4 cupped OEM tires that I drove 42000 miles on).

Thanks!